Geryon was a monstrous giant of Greek mythology, the owner of a herd of red cattle on the western island of Erytheia. Hesiod calls him the strongest of mortals and gives him three heads.

Geryon's island, Erytheia (meaning 'the red island'), was located in the far western Ocean beyond the Pillars of Heracles — the Strait of Gibraltar. The Greeks placed it at the extreme western edge of the known world, in the region where the sun sets. Some ancient sources identified Erytheia with the area around Gadeira (modern Cadiz, Spain), a Phoenician and later Greek trading settlement on the Atlantic coast of Iberia. Others treated it as a purely mythological location with no fixed geographic equivalent. The island's name connects to Geryon's famous red cattle, and its western position as

Heracles killed Geryon with an arrow poisoned with the venom of the Lernaean Hydra, the same poison that had served him since his second labor. According to Apollodorus's Bibliotheca (2.5.10), after Heracles had already killed the two-headed guard dog Orthrus and the herdsman Eurytion, Geryon armed all three of his bodies and advanced to fight. Heracles shot him with the poisoned arrow. Stesichorus's fragmentary Geryoneis (circa 600 BCE) provides more detail, describing the death of one of Geryon's three bodies with the simile 'as when a poppy sheds its petals' — an image borrowed from Homeric